Human Genetics: Concepts and Applications (Lewis), 9th Edition

Chapter 22: Genomics

Chapter Outline

CHAPTER OVERVIEW

This chapter focuses on the global effort to sequence the human genome and the genomes of a diverse collection of organisms in order to create the field of comparative genomics. A wide variety of sequencing and mapping technologies have been used to generate the data. Comparison of human genomic sequences with those of other organisms will aid the identification of disease-causing genes and offer clues to our evolutionary past. Results are confirming the complexity of the human genome. Exome research using the human reference genome (HuRef) has shown that much of the human genome is not protein encoding, a fact that may reduce genetic load. Many researchers are focusing on specific subsets of the human exome mentioned in previous chapters. The information obtained from the human genome project and others will provide new medical tools and reveal even more subtle evolutionary relationships.

CHAPTER OUTLINE

22.1 From Genetics to Genomics

  1. Genomics is the study of genomes.
Beginnings in Linkage Studies

  1. Before the Human Genome Project, positional cloning was used to identify disease causing genes.
  2. More recently, database analysis has been used to investigate interactions among multigene families.
  3. The idea to sequence the human genome emerged in the mid 1980s.
The Human Genome Project

  1. The Human Genome Project officially began in 1990.
  2. A rough draft was released in 2001 and a final sequence in 2003.
  3. The speed of the project depended upon the technological developments of automated DNA sequencing machines and DNA sequence alignment computer software.
  4. Expressed sequenced tags (EST) technology enabled researchers to focus on protein encoding genes.
  5. The project switched from mapping to sequencing in 1995, and by 1999 competition between private and public efforts intensified.
  6. The draft version of the human genome sequence was announced in 2000.
22.2 DNA Sequencing and Genome Synthesis

  1. The Sanger method of DNA sequencing involves an enzymatic extension reaction to generate complementary copies of an unknown DNA sequence.
  2. The DNA fragments differ in length by one end base. This is one of the earliest sequencing techniques that is still used to reveal the sequence of bases in the unknown DNA.
  3. DNA sequencing occurs on a vast scale today through the use of automated DNA sequencing and nanomaterials.
  4. Understanding of genome sequencing has made it possible to construct artificial chromosomes and genomes for research purposes.
22.3 Ways of Looking at Genomes

  1. Comparison of human genomic sequences with those of other organisms will aid the identification of disease-causing genes.
  2. Comparison of genomes can be used to define the minimal functional gene set for life.
  3. Comparing genomes across species can offer clues to our evolutionary past.
  4. The ENCODE Project is analyzing a random sample of 1% of the human genome.
  5. Results are confirming the complexity of the human genome.
  6. Exome research using the human reference genome (HuRef) has shown that much of the human genome is not protein encoding, a fact that may reduce genetic load.
  7. Many researchers are focusing on specific subsets of the human exome such as the diseaseome, transcriptome or pharmacogenome mentioned in previous chapters.
22.4 Personal Genome Sequencing

  1. Comparing the genomes of healthy individuals and people with diseases may
    2. provide insight into health and help individuals control risk factors.
  2. Inexpensive personal genome sequencing may be an option in the near future.
  3. Genetic technologies will impact everyone in a variety of ways in the future.
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